Karen Cameron

Dr Karen Cameron is a microbial ecologist working in the Department of Geochemistry at the Geological Survey of Denmark and Greenland. Her previous research has focused on biogeochemical interactions that occur within supraglacial and subglacial environments, and on the biogeographical variability of glacial associated microbial communities.

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Karen Cameron

Algal cells as seen through the field microscope. Examples of individual cells have been highlighted with a green circle.

For almost two months we endured (and let’s face it, enjoyed) camp life at its fullest; sleeping on the ice every night, falling into countless water filled holes, enduring the discomforts of cold-numbed toes and keeping up with the seemingly endless treadmill of camp maintenance… But at the end of the day, it was these guys, the “Ice Algae”, that were the true stars of the show!

The picture above is an image of what we see when we look down the microscope at our surface ice samples. Dark-coloured ice algae clearly dominate the sample. Typically we estimated that there were tens of thousands of algal cells in every milliliter of sample. When you bulk these samples up to liters and gallons, and then to the volume of surface ice found within biologically active area of the Greenland Ice Sheet (currently estimated at >400,000 km2), we’re looking at some serious cell numbers. As Marek Stibal explained previously, these guys are packed with a dark purple-brown pigment that protects them from sunlight, but also causes the darkening of the ice surface.

So, were we pleased with our field season? Definitely! Once we had figured out the best way to interpret the environment, we set about to amass as much data as we could, so that any conclusions that are drawn are as robust as possible. Overall we took around 600 samples for biological analysis, over 2000 close range spectral readings and, most amazingly, we individually counted around 94,000 algal cells in the field. This, on top of keeping a well-oiled camp going, kept us more than busy over the summer.

Now that we are back from our field work, our next mission is to interpret just how much albedo change is due to the darkening effect of algal growth on the ice surface, and furthermore, how much this darkening is contributing towards ice melt. In addition, we also intend to use laboratory analyses in Copenhagen to look into some of the more intricate components of the surface ice ecology that we have been living alongside all summer.

“There’s so much pollution in the air now that if it weren’t for our lungs, there’d be no place to put it all.”

Robert Orben, 1927

The dawn of the industrial revolution, in the 18th century, marked the beginning of a dramatic change in the impact that humans have on the Earth. Smoke relentlessly billowed from factories, day and night, to keep up with the ever-increasing demands on growing industries such as agriculture and textiles. By the 1850s, a secondary revolution was spurred on by technological and economic progress as a result of steam-powered ships and railways. These efforts climaxed in the mid-19th century with the momentous invention of the internal combustion engine and the generation of electricity.

“It was a town of red brick, or of brick that would have been red if the smoke and ashes had allowed it; but as matters stood, it was a town of unnatural red and black like the painted face of a savage. It was a town of machinery and tall chimneys, out of which interminable serpents of smoke trailed themselves for ever and ever, and never got uncoiled. It had a black canal in it, and a river that ran purple with ill-smelling dye, and vast piles of building full of windows where there was a rattling and a trembling all day long, and where the piston of the steam-engine worked monotonously up and down, like the head of an elephant in a state of melancholy madness….”

Of course, the abundance of smoke generated during this new mechanical era didn’t just disappear into thin air. Instead, air pollution from the burning of fossil fuels had (and has) a consequential effect on the balance of the Earth’s elements. One element that has sparked interest within the Dark Snow Project is nitrogen. When fossil fuels are burned, reactive nitrogen, in the form of nitrogen oxides (NO and NO2, referred to collectively as NOX), are expelled into the atmosphere. It is these gases that can ultimately form smog and acid rain. NOX is predominantly removed from the atmosphere through the production of nitrate (Geng et al 2014). In addition to this, a second major and historic source of human generated nitrate has come from chemical fertilizers; used to assist with the ever-increasing demands on our food resources due to our growing population. These nitrogen-based compounds have been sprayed onto our fields since the advent of the Haber Bosch process (an energy demanding reaction that enables fertilizers to be synthesized) in the early 20th century (Felix and Elliott 2013). Nitrate from farmlands can become aerolised into the atmosphere, and as a result, in addition to the increased burning of fossil fuels throughout the industrial revolution, the use of fertilizers further exasperated the generation of man-made nitrate sources.

So, if all this industrial and agricultural pollution started to occur over 200 years ago, how can we possibly know about it today? Well, once aerosolized, nitrate and NOX are transported by winds through the atmosphere until they are eventually deposited onto the Earth’s surface. Depositions that occur over the Greenland ice sheet actually become encapsulated in time, buried under layer upon layer of snow. Ice core scientists can then drill out an ice core and obtain a nifty geochemical history lesson that can span thousands of years.

Human impacts on the nitrogen cycle (Galloway et al 2008) can be detected through the use of stable isotopes (variations in the atomic mass of elements due to differing numbers of neutrons within an atom’s nucleus). 14N is the natural and most common form of the stable nitrogen element, making up over 99% of the molecules that we measure on earth. However, reductions in the rarer second form of nitrogen, 15N, has been linked to increases in human-generated NOX levels; and so has become a proxy for the impact of our fuel consumption and agricultural activities on the global nitrogen cycle (e.g. Felix and Elliott 2013, Geng et al 2014, Hastings et al 2009).

Graph by Geng et al (2014) depicting how increases in ice core nitrate levels are coupled with a decrease in 15N concentrations.

With the historic global increases of nitrate concentrations in mind, and predictions that these levels will continue to rise (Liao et al 2006), this year’s Dark Snow Project participants plan to take on an alter ego as farmers, and actually fertilize the surface of the Greenland ice sheet! The idea is to add our own sources of nitrate within fertilization plots, so that we can observe the impact that nitrate elevations have on the microbial communities of surface ice. In addition, we will be looking into the implications that changes in the microbial communities have on the lowering the surface albedo, and of course, ultimately enhancing ice sheet melt rates.

Dr Karen Cameron is a microbial ecologist working in the Department of Geochemistry at the Geological Survey of Denmark and Greenland. Her previous research has focused on biogeochemical interactions that occur within supraglacial and subglacial environments, and on the biogeographical variability of glacial associated microbial communities.

Works Cited

Felix J D and Elliott E M 2013 The agricultural history of human?nitrogen interactions as recorded in ice core 15N?NO3?Geophysical Research Letters 40 1642-1646